Molecularly imprinted poly(methacrylic acid) based QCM biosensor for selective determination of L-tryptophan

In the present work, molecularly imprinted polymer (MIP) for L-tryptophan was synthesized using bulk polymerization method. A highly selective and sensitive biosensing method for the amino acid was developed using quartz crystal micmbalance (QCM) biosensor. The molecular imprints were synthesized through in-situ method using poly(methacrylic acid) (PMAA) macromolecular network. Successful imprinting was confirmed through Fourier infrared spectroscopy (FTIR). The dynamic adsorption and Scatchard analysis were used to understand the effect of various imprinting parameters on the final structures. The molecularly imprinted polymer sample with 10 mmol of ethylene glycol dimethacrylate (EGDMA) crosslinker exhibited a high adsorption about 12 mg/g towards L-tryptophan. The morphological analysis of imprinted structures was studied using scanning electron and atomic force microscope techniques as well. Further, the optimized MIP pre-polymer solution has coated on QCM electrode surface and sensing studies was conducted using different concentrations of L-tryptophan. The limit of detection was determined as 0.73 ng/mL. The biosensor found highly selective and not responded to the presence of structural analogous of L-tryptophan such as D-tryptophan and ascorbic acid. The MIP modified QCM biosensor exhibited high selectivity coefficients towards L-tryptophan about 7.3 and 12 with respect to the analogous. Further, the proposed MIP-QCM sensor was successfully applied to the determination of Tryptophan in real sample analysis such as food and urine samples with excellent recoveries ranging (97-104 %).